We estimate that "50 Shades of Grey" has grossed about $440 million since it first went on sale. The 30 million books sold in the last quarter have grossed at least $330 million—before costs, expenses and distributions fees—for Bertelsmann. That's more than a third of Random House's sixth-month revenues for the year.

However, all of the green didn't come solely from 50SoG. Random House also had another 152 books on the New York Times best-seller list. Among those is George R.R. Martin's best-selling "Songs of Ice and Fire" series, the inspiration behind HBO's hit "Game of Thrones."